1. Field of the Invention
The invention relates to an article of footwear, i.e., a boot or shoe, for example, that is adapted for use for walking or running, particularly over mountainous terrain. More particularly, the invention relates to a sole or bottom assembly designed for such an article of footwear.
2. Description of Background and Relevant Information
FIGS. 1-4 illustrate problems related to the use of conventional shoes for running, especially in the mountains or uneven terrain.
Initially, running shoes are generally designed with shock-absorbing means, particularly in the heel area, for absorbing the repeated impacts that are generated during the stride, or in other areas the shoe that receive the most severe impacts, so as to avoid micro-traumatisms on the user's joints.
Typically, as shown in FIG. 1, such a shoe 10 has an upper 11 mounted on a bottom assembly 12, which bottom assembly has a midsole 13 made of a shock-absorbing material and a walking sole 14. The bottom assembly 12, seen in transverse cross-section, is substantially trapezoidal, with an acutely shaped, or sharp, edge 15. As a result, during lateral or medial bending of the foot or of the leg, the midsole 13 partially absorbs the additional forces by being compressed.
Once this midsole 13 is completely compressed, the shoe tends to tilt suddenly in relation to its edge 15 and can then cause injuries (sprains, etc.).
FIG. 2 shows another type of known shoe 10 which, like the shoe of FIG. 1, has an upper 11, a bottom assembly 12 having a shock-absorbing midsole 13, and a walking sole 14.
In this second type of shoe, described in U.S. Pat. No. 4,322,895, the object is to avoid the aforementioned shoe tilting problems by having the midsole rise along the upper. However, this second type of shoe has the same drawback of sudden tilting once the layer of the midsole 13 is completely compressed.
Furthermore, running shoes are generally designed to cooperate with flat terrain on which running events generally take place. However, the development of sporting contests of the “raid” type, including various sporting activities taking place in a mountainous environment, and including foot races in the mountains, in particular, involve new constraints on the shoes and the users. Indeed, foot races in the mountains generally take place on hilly, sloping, non-“planar” surfaces, i.e., those having numerous asperities, rocks, and which can even have slants, i.e., transverse slopes in relation to the main direction of the race.
Because only few running shoes actually provided for such conditions are commercially available, there are numerous traumatic problems and risks of accidents for the runners.
FIGS. 3 and 4 show the behavior of the conventional shoes shown in FIGS. 1 and 2 on sloping terrains, and particularly on slanting terrain, i.e., having a slope in the transverse direction in relation to the main direction of the race.
In each of these cases, the bottom assembly 12, 22, respectively, of each shoe 10, 20, respectively, deforms slightly depending upon the slope of the terrain, but insufficiently, such that the vertical median plane T of the upper remains very inclined with respect to the vertical plane V, i.e., with respect to a plane perpendicular to the horizontal, and that the shoe tends to slide in a direction G along the slope.
At the end, the angle β, created by the median vertical plane T of the upper relative to the vertical plane V, corresponds to the slant angle of the slope.